1. Field of the Invention
The present invention relates to an apparatus and method for controlling output power of a combination hood and microwave oven, and more particularly, to an apparatus and method for controlling power of a combination hood and microwave oven, wherein an output level of a high voltage transformer for generating a high voltage can be adjusted.
2. Background of Invention
Generally, a combination hood and microwave oven generates a high-frequency output power lower than that of a table microwave oven. This is because there is a limitation on the usable amount of current in the combination hood and microwave oven and the limited amount of current should be distributed into those for use in drive of a vent fan, an electric lamp and all components for controlling the microwave oven such as a turntable and a magnetron.
However, the table microwave oven does not require a certain amount of current for use in the drive of the vent fan and electric lamp contrary to the combination hood and microwave oven. Therefore, in the case of the table microwave oven, a greater amount of current can be assigned to the magnetron as compared with the combination hood and microwave oven. Consequently, the high-frequency output power of the table microwave oven can be generated greater than that of the combination hood and microwave oven.
FIG. 1 shows a control configuration for control of output power of a conventional combination hood and microwave oven.
In the conventional combination hood and microwave oven, as shown in the figure, a vent fan 9, an electric cook top lamp 13, a turntable 17 and a high voltage transformer 21 for generating a high-frequency output voltage for a magnetron (not shown) are connected in parallel to an electric power supply inputted through a power supply terminal 1 so that they are supplied with electric power.
The control configuration also has additional control relays 7, 11, 15 and 19 so that supply of the electric power can be made through control of the relays.
The microwave oven constructed as such is set to use the rated amount of current, and a fuse 3 selected depending on the rated amount of current is connected to the power supply terminal 1. Thus, it is constructed in such a manner that if the amount of current produced from such a configuration exceeds a predetermined value of the fuse 3, the fuse 3 is gone to cut off the supply of the electric power.
Meanwhile, a conventional high voltage transformer (HVT) 21 is constructed such that a voltage V2 at a secondary side of the transformer 21 is determined according to a voltage V1 applied to a primary side of the transformer, as shown in FIG. 2. Further, the high voltage transformer 21 is designed in consideration of remaining power consumption except power consumption related to use of respective components of the combination hood and microwave oven shown in FIG. 1 from the electric power usable for the microwave oven.
That is, when the electric power is applied to the primary side of the high voltage transformer 21, a high voltage is induced at the secondary side thereof. Such an induced voltage is transferred to the magnetron (not shown) which in turn oscillates. At this time, the magnitude of output power of the magnetron is determined according to the voltage at the secondary side of the high voltage transformer 21. In other words, the higher the induced voltage at the secondary side is, the higher output power of a high-frequency wave generated by the magnetron is.
Furthermore, the voltage at the secondary side of the high voltage transformer 21 is obtained from the following relationship (1):n2/n1=V2/V1,  (1)
where V1 is the voltage at the primary side of the transformer, n1 is the number of windings of a primary coil, V2 is the voltage at the secondary side of the transformer, and n2 is the number of windings of a secondary coil.
Therefore, in order to obtain a higher voltage at the secondary side of the high voltage transformer 21, the transformer should be designed such that the number of windings of the secondary coil is increased or the number of windings of the primary coil is decreased.
Through such a process, the high voltage transformer for use in the conventional combination hood and microwave oven is designed in consideration of remaining power consumption except power consumption of all components within the microwave oven. The high voltage generated by the high voltage transformer of the combination hood and microwave oven designed as such is inevitably lower than that generated by a high voltage transformer provided in the conventional table microwave oven. As described above, this is because the table microwave oven does not include components such as the vent fan and the electric lamp contrary to the combination hood and microwave oven.
Thus, the conventional combination hood and microwave oven has the following problems.
First, since the high voltage to be supplied to the magnetron is inevitably lower than that of the table microwave oven, the conventional combination hood and microwave oven inevitably has low cooking performance upon cooking in the microwave oven which requires very high output power. In particular, there is inconvenience in that it takes a long time to perform cooking.
Second, even though all the components are not always operated at a time in the combination hood and microwave oven, the high voltage transformer always generates a constant output level due to its product specification. This leads to a problem of inefficient use of the product.
Third, although an inverter for controlling the high output power has been employed in the combination hood and microwave oven in connection with the above matter, this results in increase of its production costs, thereby increasing a burden of a consumer on its price and leading to decrease in purchasing power of the consumer for the product.